The Race for Batteries

EE Times

Though they started their research on future battery materials only past April, they already have achieved potentially seminal results: A research team at the Technical University of Graz (Austria) succeeded in providing fundamental data on the nuclear dynamics of a specific ion conductor that could greatly improve the characteristics of lithium-ion batteries.

Not only the development electromobility but also the design of more powerful smartphones and portable computers pose high challenges to battery systems: Engineers and not least customers expect the energy storage to offer increased capacity and safety as well as better longevity. Towards this end, solid-state lithium batteries are among the white hopes of battery research. In comparison to conventional lithium-ion batteries with liquid electrolytes, solid-state batteries feature superior characteristics with respect to safety, service life and thermal stability. For this reason, scientists from disciplines such as solid-state chemistry, physics and materials sciences are searching feverishly for solid-state ion conductors suitable for use in such batteries.

In his dissertation work, Viktor Epp from the Institute of Chemical Technologies and Materials of the Graz Technical University scrutinized a specific sulphide: Li6PS5Br. He got granular on this material by submitting the material to lithium nuclear magnetic resonance spectroscopy and could solidify the results of earlier and more tentative works: The lithium ions in the sulphide at hand move incredibly fast. This qualifies the material as a front-runner among solid-state electrolytes for usage in batteries.

Epp observed more than a billion "ion jumps" per second at normal ambient temperature. This translates into enormous charge carrier mobility, one of the fundamental properties of a promising material.

Such a high carrier mobility has already been verified in other lithium-based chemical combinations. However, many of these materials are not only ion conductors but also electron conductors which disqualifies them for the use as solid-state electrolyte.

At first sight, the principle of electrochemical energy storage in a lithium-ion battery seems to be simple: During the process of charging and discharging a battery, the ions move between the battery poles and during this journey they cross materials which are different in structure. In a solid-state lithium-ion battery, a solid matter such as an oxide that contains lithium or a sulphide, assume the task of the conduction electrolyte. "The more we know about the nature of charge carrier transport in solid-state material, the better we know which materials are best suited for the further development of batteries", says Martin Wilkening from the Christian Doppler Laboratory of the he Institute of Chemical Technologies and Materials of the Graz Technical University.

Christoph Hammerschmidt writes for the EE Times, from where this article is adapted